c/hplc wiki

What this community is for

The analytical deep end: RP-HPLC methods, gradient design, integration decisions, LC-MS confirmation, amino-acid analysis, water content, and why two labs can report 98.1% and 96.4% on the same vial and both be right. Post the chromatogram, not the summary line.

c/hplc was created on 14 Sep 2023 and currently has 31,700 members and 130 captured submissions. It sits in the busiest tier of the site, which mostly affects how fast a question gets answered rather than how well.

Rules, and why each exists

Community rules come first, then the six site-wide rules that apply everywhere on GLP Research Hub. Community rules are enforced by the moderators listed at the bottom of this page; site rules are enforced by everyone.

1. Chromatogram or it did not happen. Axis labels included.
2. State the method: column, gradient, detection wavelength, injection volume.
3. Area% is not mass%. Posts that conflate them get a correction flair, not a removal.

And the site rules, which are short on purpose:

1. Independent community. Nobody here sells anything, and anyone who tries is banned.
2. Not medical advice. Describe what you did; never prescribe to a stranger.
3. Claims need evidence. Batch numbers, dated screenshots, independent test reports, or a citation.
4. No referral links, discount codes or affiliate URLs. Permanent ban, no appeal.
5. No contact handles, wallet addresses or tracking numbers — they identify people.
6. Be recognisably decent. Disagree hard, insult nobody.

Terms you will see

Vocabulary that turns up constantly in c/hplc. Each links to the topic page, which collects every submission that touches it.

• HPLC — high-performance liquid chromatography — the workhorse separation method here.
• chromatogram — the raw detector trace. Post it; the summary line hides the interesting parts.
• gradient — the changing mobile-phase composition that separates the peaks.
• LC-MS — chromatography plus mass spectrometry; the method that answers identity.
• integration — deciding where each peak starts and stops — where a lot of the number comes from.
• purity — usually area% from a UV chromatogram: how much of what the detector saw was product.
• method development — building a separation that resolves what you care about.

Start here

The twelve highest-scoring submissions in this community. Not necessarily the most correct — the most agreed-with, which is a different thing, and worth remembering when you read them.

1. [Lab] SGN cagri — VendorInvestigate came back 93.7% against a claimed 94.2% — 14k points, 34 comments, 2 years ago
2. am I the only one who found method development harder than the injections — 14k points, 41 comments, 2 years ago
3. tried HPLC for 5 weeks. here is what happened. — 13k points, 30 comments, 1 year ago
4. [Meta] the method development rule is doing its job and people should stop complaining — 12k points, 17 comments, 2 years ago
5. 21 months in and HPLC is still the thing I get wrong — 8.8k points, 51 comments, 11 months ago
6. [Question] Ireland — has anyone got a straight answer on chromatogram — 8.8k points, 34 comments, 2 years ago
7. Spain: gradient, and what it actually costs here — 8.4k points, 34 comments, 1 year ago
8. [Lab] 24th independent test on QSC, and the trend is the interesting part — 8.1k points, 32 comments, 8 months ago
9. [Question] how do you actually verify LC-MS — 8.1k points, 41 comments, 2 years ago
10. LC-MS: what the trials say vs what this community says — 7.9k points, 34 comments, 6 months ago
11. [Question] how do you actually verify gradient — 7.3k points, 53 comments, 2 years ago
12. reading purity threads from 2024 and half of it aged badly — 7.3k points, 41 comments, 5 months ago

Asked constantly

• two labs, same vial, 98.1 and 96.4. both right?
• peak at 4.2 min, nobody can tell me what it is, ideas
• two labs, same vial, 98.1 and 96.4. both right?
• [Question] what is a reasonable system suitability RSD for this work
• [PSA] integration is not what most of this community thinks it is
• does gradient actually matter or is it forum lore at this point
• my eGFR moved and I cannot work out whether LC-MS is why
• my A1c moved and I cannot work out whether method development is why
• why does nobody talk about chromatogram
• unpopular opinion: purity is massively overrated

If your question is on that list, read the answers there first. If it is not, ask it — that is what the community is for, and "this has been asked" is only a helpful reply when it comes with a link.

Who runs this

Moderation here is done by volunteers who also post as normal members. They are not clinicians, not vendors, and not paid.

• u/sig_figs_sam — c/hplc mod. Analytical chemist by trade. Round your numbers responsibly.
• u/hplc_hobbyist — Bought a second-hand HPLC and a lifetime of regret. I post chromatograms, not conclusions.
• u/peak_area_pete — Area% is not mass%. I will keep saying this until the sun goes out.
• u/mass_spec_maggie — LC-MS/MS is my day job. Peptide mapping is my hobby. Both are the same job.